Indicating system



Nov. 30, 1948.

G. E. VALLEY, JR

INDICATING SYSTEM Filed Nov. 4, 1944 FIG-2 FULSES FROM TIMER FL/B-FLOP GA TE x-swssp v01; TAGE h -DELAY GATE Y-SWEEP VOLTAGE 5 mm mm W M .4 R L E 6 w E W T mod'e Bray acscilloscope "rather than by" discrete range Patented Nov. 30, 1948- mplczrrmesvs rmvr by unesne assignment America as rrepresente Cambridge, Mass assignor, s, damthe -.United States of d by-dahe Secretaryof-War Application-"November 4, lii' i ijas'erial No; 561 9911 invention "relates sto iel ectronic :rindicators for sra'dio object locating systemsar :1ike.:appamains and "particularly to the sweep circuits, of th'e #eatho'deray oscillo'scopes 'utilize'dr in airborne iradiofobiect-locatingaequipment.

Where a visual indication. of the i-approa'ch ;oi

aircraft to 'atargetlis used-as .-a .tactical or navigat-irmal ai'd, lit iriay the idesiriable, sincorderyito -obta"in ztheenecessary degree-of accuracy, .that -th'e1qpenator changelthe irange scale on the cathwhereby the range of the r-system :iis :shozitened has lithe z aircraft .nears its target. 1 w v Heretofore it hast-been the practice to change 'trairgei-settings azby manipulation 013 a switching 'i'deviceior the like, thereby to alter certain cirwait :rparameters :in .a.-definite :step or series of rsteps. aQcoasionally in such azsy tem, Whenthe coperatorswitches to a shorter range the target 'has been lost :momentarily due to the disturblaHIlOBOfdih-GOHTSUHS affected by thechange. v

.Iti-iswagprimary object of the, present invention to provide a circuitfor effecting. asmooth step- :=-1ess transition from one range settingto another :of the indicatingsystem so that interruption of thecfunctioning of the various circuits w ilfbe obviated. a N a, =The-,presentinvention hasbeen developed .particularly-for lthe purpose. of .improv'ing th operlation of airborne ra merit of the l-type which provide ssa "map-like spresentaiiion lot .the .;areas being -scanne i on .a cathode ray oscilloscope. Alinearf iX-fs'wep and a -.-hyperbolic Y-sweepare incorporated in the indicator circuit, and it is contemplated that as the range is *varied, .-the time variation or slope of each of these sweeps will be varied ac- 'cbidirrg'lyj 'Thus, another amateur -the invention is to vary both the X and Y-scales in a'continutrol. However, it will be appreciated that the ie'veri'fit is desire'd' to 'accoxnplish range expansion .ofcontraction'as' atsmOoth,continuous operation intervals;

In the drawings:

Fig. 1 is a, schematic circuit diagram illustrating the application of one embodiment of this invention to a typical indicator circuit; and

Fig. 2 comprises a set of timing diagrams showing the relation between various voltage pulses in the circuit illustrated in Fig. 1.

Referring to Fig. 1, a circuit is shown for providing X-sweep and Y-sweep voltages, which are respectively applied to the horizontal and vertical deflecting plates 5 and 6 of a cathode did 0153 ec't locati'ng iequip- 25 plate connected to team. (0!..3'1 5424).

irayx'tuhe 11. It will :be understoodhowevmt, that adeflecting 'coils,1-instead of plates, may be'used. tithe portion .of :the circuit for producing the .tX-sweepwoltage 'siS shown in .the upper part of .iFig. t1. lThe cathode of .a .triode .8 is connected througha resistor 9 to toneside of Va conden'serflifi, the otherside of this condenser being grounded. The "plate of 'the tube 8 is connected toa suitable source of positive voltage-(not "shown). Aswillbedescribed hereinafter, a. variable positive potential is applied to'the grid 0f *the tube 8 for "a purpose which will be explained later. The-grid of-a triode 'H is connected-to a point 1'2 at the junction of resistor and condenser I 0. The tube l --is-utilizedas a 5 cathode follower, the cathode o'f this tube'being connected by a load' resistor 43 to ground and the plate thereof being connected to a positive "woltage source. 'The deflecting voltage forflthe X-sweep is obtained from 'the 'load resistor d3 0 and, after being passed through a sweepvampli- "fier I 4 'is applie'd -to the horizontal deflecting =plates 5 ='of=- thecathode ray tube 1.

Normally the condenser N] is effectively shortcircuited'by a =c1amping tube 15 which has alts junction point 1.12, and its cathode connected to ground. The initiation 'of the X-sWeep -is: accomplished. by applying a negative pulsezfroma conventional flip-flop circuit Knotshown') to :thegrid of thetube [5. This 30 'biases thetubei'lfi to cut-.ofi and thereby removes :theJ-short circuit ifromthe condenser II]. The condenser 1H] thereupon commences to charge, aand f as the voltage across this tcondenser .builds vu-p; it is amplified by the cathode follower I Is. and fithe-rsweepramplifier It. ?For the purpose, of makingit'he t-charging characteristic of the conde'nser rillsubstantially'linear;a feedback path is afforded ytthroughaicondenser [6 which connects the cathmdeiofz tubeil l' to :thegcathode of tube 8. Normal- .ttheutube '15, IthB COHdGHSBI' i5 .is charged-to a voltage substantially equal to the drop through qlthesi're'sistor. 9; The capacity of the condenser L6; chosen sufficiently large in comparisomwith ithati ofccondenser til :so'thatthe time constant of condenser l6 and its associated circuit is large compared with the sweep period of the cathode ray tube. As the voltage across the cathode follower load resistance l3 increases, the voltage level at the junction point I! of the condenser l6 and cathode of tube 8 is gradually raised thereby producing a substantially linear voltage variation with respect to time instead of one which follows an exponential curve.

The portion of the sweep circuit which produces the Y-sw'eep is shown in the lowi part of Fig. 1 and is substantially identical to the X- sweep portion except that in place of the single condenser I 0, a resistance-capacity network generally designated 20 is utilized for producing a hyperbolic time variation of voltage. Corresponding elements in the X-sweep and Y-sweep portions are numbered alike except for the addition of primes to the reference characters thereof. The condenser I6 serves to insure a true hyperbolic sweep as the network 20 is charged.

Referring to Fig. 2, pulses from a suitable timer are employed to trigger a flip-flop circuit (not shown) at regular intervals. A negative gate generated by this circuit is applied to the grid of tube I5 thereby initiating the X-sweep. Similarly, the application of a negative gate to the grid of tube [5' shuts this tube off and initiates the Y-sweep. However, the Y-sweep must be delayed in relation to the initiation of the X-sweep in order to compensate for the height of the aircraft, as is familiar to those skilled in the art. Such time delay may be accomplished in the circuit which forms these gates. When the Y- sweep voltage attains a predetermined amplitude, which is fixed for all ranges, action takes place in the circuit to terminate both the X- sweep and the Y-sweep simultaneously by removing the negative gates from the grids of the clamping tubes l5 and I5, thus restoring the circuit to its normal condition until the succeeding timing pulse occurs. Anyvsuitable means well known in the art may be employed to effect this terminating action and disclosure thereof is not believed essential to the present invention.

For a given range there is a definite time required for each of the X and Y-sweeps to traverse the cathode ray tube screen; or in other words, a certain time should elapse during which the controlling sweep voltage (in this instance the Y-sweep) builds up to the predetermined level. To change the scale of the map presen tation on the scope, it is necessary that the time in which the sweep voltage attains this limiting amplitude be varied; that is, the slope of the voltage-time characteristic is given greater or less value depending upon Whether the presentation is to be enlarged or diminished. In the present instance the change in the voltage build- .up rate is accomplished by changing the positive bias on the grids of the tubes 8 and 8'. A

T potentiometer 2! is provided for this purpose,

both of these grids being electrically connected to the movable contact member'of the potentiometer. Varying the positive bias in this'manner eifects a continuous variation in the initial voltage which is impressed on the resistancecapacity networks Q-Ifland 920 when the respective clamping tubes and I5 are cut oil,

"thereby smoothly altering the sweep speeds.

An outstanding advantage of the potentiometer arrangements for varying the range of the system is that it minimizes the disturbing effects upon the sweep circuit and enables smooth range expansion or contraction to be performed by the operator. Thus the likelihood of losing the target during changeover from one range to another is greatly reduced, if not eliminated. This is of great advantage in bombing operations, for example, as the target is being approached. Other applications will readily occur to those skilled in the art.

While I have illustrated and described a selected embodiment of my invention it is apparent that variations and modifications may be made without departing from the spirit of the invention. Hence I do not desire to limit the invention to the precise details described herein but wish to avail myself of all improvements and modifications within the purview of the following claims.

I claim:

1. In a variable range radio object-locating system indicator having a cathode ray tube provided with horizontal and vertical deflecting elements,the combination of, horizontal and vertical sweep control means including resistance and capacitance elements, said means determining the sweep speeds in accordance with the rate of charge of said capacitance elements, voltageapplying means including a plurality of electron tub-es for impressing charging voltages respecrate of charge of a capacitance element in one -file of this patent:

of said resistance-capacity networks, means for r determining the vertical sweep speed in accordance with the rate of charge of a capacitance ele ment in the other of said resistance-capacitance networks, means including a plurality of electron tubes for applying charging voltages to said capacitance elements, and a potentiometer for simultaneously varying the grid bias of said electron tubes to effect stepless variations in said charging voltages.

' GEORGE E. VALLEY, JR.

REFERENCES CITED" H The following references are'of, record in the UNITED STATES PATENTS Number Name 1' Date,

2,305,930 Martinelli Dec. 22,1942 2,315,848 Geohegan Apr. 6, 1943 2,350,069 Schrader et a1. May 30, 1944 

